1,269 research outputs found
Lifshitz-Slyozov Scaling For Late-Stage Coarsening With An Order-Parameter-Dependent Mobility
The coarsening dynamics of the Cahn-Hilliard equation with order-parameter
dependent mobility, , is addressed at
zero temperature in the Lifshitz-Slyozov limit where the minority phase
occupies a vanishingly small volume fraction. Despite the absence of bulk
diffusion for , the mean domain size is found to grow as , due to subdiffusive transport of the order parameter
through the majority phase. The domain-size distribution is determined
explicitly for the physically relevant case .Comment: 4 pages, Revtex, no figure
RNA Sequencing Reveals Novel Transcripts from Sympathetic Stellate Ganglia During Cardiac Sympathetic Hyperactivity.
Cardiovascular disease is the most prevalent age-related illness worldwide, causing approximately 15 million deaths every year. Hypertension is central in determining cardiovascular risk and is a strong predictive indicator of morbidity and mortality; however, there remains an unmet clinical need for disease-modifying and prophylactic interventions. Enhanced sympathetic activity is a well-established contributor to the pathophysiology of hypertension, however the cellular and molecular changes that increase sympathetic neurotransmission are not known. The aim of this study was to identify key changes in the transcriptome in normotensive and spontaneously hypertensive rats. We validated 15 of our top-scoring genes using qRT-PCR, and network and enrichment analyses suggest that glutamatergic signalling plays a key role in modulating Ca2+ balance within these ganglia. Additionally, phosphodiesterase activity was found to be altered in stellates obtained from the hypertensive rat, suggesting that impaired cyclic nucleotide signalling may contribute to disturbed Ca2+ homeostasis and sympathetic hyperactivity in hypertension. We have also confirmed the presence of these transcripts in human donor stellate samples, suggesting that key genes coupled to neurotransmission are conserved. The data described here may provide novel targets for future interventions aimed at treating sympathetic hyperactivity associated with cardiovascular disease and other dysautonomias
A small-specimen investigation of the fracture toughness of Ti 5 Si 3
The fracture toughness of the refractory hardmetal Ti 5 Si 3 , with a grain size between 5 and 6 μm, was measured using the controlled-flaw method in conjunction with the miniaturized disc-bend test. The specimens used in these experiments were 3 mm diameter and varied in thickness from 150–450 μm. They were indented using a Vickers pyramid indentor to indention loads varying from 2.9–79.2 N. Indentation cracking was experienced at all indentation loads, and R -curve behaviour was exhibited. The fracture toughness was determined to be 2.69 ± 0.21 MPam 1/2 using a straightforward graphical procedure involving an empirical R -curve equation. This value is almost 30% higher than that of similar material (2.1 MPam 1/2 ) with a larger grain size, suggesting that the fracture toughness of this material, which fractures intergranularly, might be grain-size dependent.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44735/1/10853_2004_Article_BF00351561.pd
Defect and solute properties in dilute Fe-Cr-Ni austenitic alloys from first principles
We present results of an extensive set of first-principles density functional
theory calculations of point defect formation, binding and clustering energies
in austenitic Fe with dilute concentrations of Cr and Ni solutes.Comment: 24 pages, 10 figures, published in Phys. Rev.
The Mechanisms of Codon Reassignments in Mitochondrial Genetic Codes
Many cases of non-standard genetic codes are known in mitochondrial genomes.
We carry out analysis of phylogeny and codon usage of organisms for which the
complete mitochondrial genome is available, and we determine the most likely
mechanism for codon reassignment in each case. Reassignment events can be
classified according to the gain-loss framework. The gain represents the
appearance of a new tRNA for the reassigned codon or the change of an existing
tRNA such that it gains the ability to pair with the codon. The loss represents
the deletion of a tRNA or the change in a tRNA so that it no longer translates
the codon. One possible mechanism is Codon Disappearance, where the codon
disappears from the genome prior to the gain and loss events. In the
alternative mechanisms the codon does not disappear. In the Unassigned Codon
mechanism, the loss occurs first, whereas in the Ambiguous Intermediate
mechanism, the gain occurs first. Codon usage analysis gives clear evidence of
cases where the codon disappeared at the point of the reassignment and also
cases where it did not disappear. Codon disappearance is the probable
explanation for stop to sense reassignments and a small number of reassignments
of sense codons. However, the majority of sense to sense reassignments cannot
be explained by codon disappearance. In the latter cases, by analysis of the
presence or absence of tRNAs in the genome and of the changes in tRNA
sequences, it is sometimes possible to distinguish between the Unassigned Codon
and Ambiguous Intermediate mechanisms. We emphasize that not all reassignments
follow the same scenario and that it is necessary to consider the details of
each case carefully.Comment: 53 pages (45 pages, including 4 figures + 8 pages of supplementary
information). To appear in J.Mol.Evo
Change of tRNA identity leads to a divergent orthogonal histidyl-tRNA synthetase/tRNAHis pair
Mature tRNAHis has at its 5′-terminus an extra guanylate, designated as G−1. This is the major recognition element for histidyl-tRNA synthetase (HisRS) to permit acylation of tRNAHis with histidine. However, it was reported that tRNAHis of a subgroup of α-proteobacteria, including Caulobacter crescentus, lacks the critical G−1 residue. Here we show that recombinant C. crescentus HisRS allowed complete histidylation of a C. crescentus tRNAHis transcript (lacking G−1). The addition of G−1 did not improve aminoacylation by C. crescentus HisRS. However, mutations in the tRNAHis anticodon caused a drastic loss of in vitro histidylation, and mutations of bases A73 and U72 also reduced charging. Thus, the major recognition elements in C. crescentus tRNAHis are the anticodon, the discriminator base and U72, which are recognized by the divergent (based on sequence similarity) C. crescentus HisRS. Transplantation of these recognition elements into an Escherichia coli tRNAHis template, together with addition of base U20a, created a competent substrate for C. crescentus HisRS. These results illustrate how a conserved tRNA recognition pattern changed during evolution. The data also uncovered a divergent orthogonal HisRS/tRNAHis pair
Thinking the unthinkable: Imagining an ‘un-American,’ Girl-friendly, Women- and Trans-Inclusive Alternative for Baseball
The purpose of this article is twofold: to capture the injustice inherent in the gendered bifurcation of baseball and softball via the prism of critical feminist sport studies; and to begin to imagine a girl-friendly/women-and trans-inclusive future for baseball that is less fertile for cooptation into post-911 United States security state discourses. In this article I link the "unthinkability" of the occupational segregation of baseball in North America to the dominance of the ideology of the two sex system and European disasporic morality. To illustrate the extent of this occupational segregation via the gendered bifurcation of baseball and softball, I draw on feminist sport studies to examine the exemplars or "texts" of three Canadian brother/sister baseball softball duos: Jason Bay and Lauren Bay Regula; Brett and Danielle Lawrie; and Mathew and Katie Reyes
Numerical simulation of diffusion-controlled droplet growth: Dynamical correlation effects
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